Many modern plastics lack sufficient strength for use as structural materials. The reinforcement of otherwise unsuitable plastics with fiber of glass, boron, graphite, and metal is known in the art. Reinforced plastics are replacing conventional materials in a variety of applications, including load-bearing structural members. The shift in choice is based on economic advantages, simplified fabrication, freedom from corrosion, and lower weight. One method of preparing reinforced plastics involves embedding tensioned glass fibers in a plastic matrix. The art discloses that reinforced plastics have improved strength and structural integrity. Other important properties not disclosed in the art include impact resistance and elongation properties. The preparation of stronger, lighter materials with impact resistance and elongation properties is a highly desirable objective.
U.S. Pat. No. 3,817,806, issued to Anderson et al., discloses a method for prestressing reinforced thermoset resins. Fibers held under tension are encapsulated with thermosetting resin. The reinforced resin may be formed into rigid structures. The patentees disclose the use of fiberglass fibers with ester based, acid based, or amine based resin. Shaped material prepared by the disclosed method are said to have structural integrity and a tendency to resist deformation.
U.S. Pat. No. 3,709,754, issued to Medler, discloses a method of preparing construction members of glass fibers impregnated with a hardened resin. Layers of glass fiber fabric impregnated with a hardenable resin are wrapped around glass fiber rods bounded together under tension with hardened binder resin. Construction members prepared by the disclosed method demonstrate high strength and resistance to lateral bending and flexing.
U.S. Pat. No. 3,686,048, issued to Schertzinger, discloses a process for preparing multilayer fiber reinforced structures. Parallel fibers are bonded together under tension with a small amount of thermoplastic or thermosetting resin and heated to form a flexible sheet. The sheet comprises a web of fibers connected by resin bridges. A liquid thermoplastic or thermosetting matrix is applied to single or multiple layers of the reinforcing sheets to form fiber reinforced structures. The patentee specifically discloses the preparation of sheets with glass fibers.
U.S. Pat. No. 4,124,670, issued to Cecka et al., discloses a structural member consisting of an expanded formed plastic core and resin-coated graphite fibers. A process for making the structural member is also disclosed. A foam core composition is prepared by blending a resin component, a curing agent, a blowing agent, and a low density filler material. The core composition is formed into an elongated core strip which is wrapped with resin-coated unidirectionally oriented graphite fibers. The core strip is expanded under pressure to form a structural member suitable for tennis racket frames. The structural member demonstrates light weight, high strength, and stiffness.